Multi-contact switch



April 3, 1956 R. D. HANCOCK 2,740,851

MULTI-CONTACT SWITCH Filed Jan. 8, 1951 2 Sheets-Sheet l 1 3 I. WIQMMLQI'IISJIR! 2 I Ii 44 //VV(f/V702: 1206627 0. #4/VC'0CK #49 44rwr Arron NE) April 3, 1956 HANCQCK 2,740,851

MULTI-CONTACT SWITCH Filed Jan. 8 1951 2 Sheets-Sheet 2 United States Patent 2,740,851 Patented Apr. 3, 1956 fiicc NIULTI-CONTACT SWITCH Application January 8, 1951, Serial No. 204,954 2 Claims. (Cl. 200-6) This invention relates to a multi-contact switch.

Switches that display a large number of stable positions have heretofore occupied a relatively large physical volume. Normally the individual contact points are distributed equi-distantly on an arc about a central point. A wiper contact rotates on an axis through this central point such that each of the individual contact points are accessible to the wiper contact. Since each of the individual contact points must be insulated from each other, an increase of the number of individual contact points necessitates an increase of the radius or length of the are on which they are disposed.

It is, accordingly, an object of this invention to provide a configuration of switch contacts such that a minimum of volume per switch is approached.

The foregoing object is accomplished, in short, by imbedding contacts in a material that displays a desired dielectric characteristic, such that they form a spiral, and so disposing a suitable wiping or sliding contact that it can be guided to move over the entire length of the spiral of contacts as desired.

This invention possesses other objects and features, some of which, together with the foregoing, will be set forth in the following description of several preferred embodiments of the invention. The invention will be more fully understood by reference to the attached drawings illustrating these embodiments, in which:

Figure l is a simplified plan view of a switch embodying one form of the present invention.

Figure 2 is a cross sectional view of the embodiment illustrated in Figure 1.

Figure 3 is a simplified plan view of another embodiment of the present invention.

Figure 4 is a cross sectional view of the embodiment illustrated in Figure 3.

Figure 5 is a top plan view of a third embodiment of the present invention.

Figure 6 is a view partly in section and partly in elevation taken as indicated by line 6-6 in Figure 5.

Referring first to Figure l, a ribbon or sheet of material is shaped such that it takes the configuration of an Archimedean spiral, for example, and is employed as a vertical wall 1. Supporting the wall 1 is a body 2, of a nonconducting, solid dielectric material in which spiral wall 1 is imbedded to provide a spiral channel, in the bottom of which a plurality of contact pegs 3 is inserted to extend through body 2. The wall 1 may be fashioned of thin steel, aluminum, copper, or the like, and the body 2 may be formed of glass, porcelain, or a plastic, for example. Contact pegs 3 are positioned on a center line between adjacent convolutions of the wall 1 and are disposed perpendicularly to the surface of the body 2 as shown in Figure 2. The tops of pegs 3 constitute the stationary contacts of a switch embodying the present invention.

A wiper 9, mounted in a follower 6 which is slidably connected to an arm 5 by means of a guide pin 7, is formed of a conducting material that is preferably similar to the material employed in forming the pegs'3, so that the contacts will not corrode or display any undesirable contact or thermal potentials. The arm 5 is rotatably connected to the body 2 by means of a center post 4. The arm 5, the center post 4, the follower 6 and the guide pin 7 may be fashioned from a conducting material, such as copper, in order to provide a circuit from the wiper 9 to a non-rotating wiper lead 11. An individual peg lead it) is attached to each peg 3; the connections being made at the lower ends of the pegs. Thus a complete electrical circuit can be made between the wiper lead 11, which is attached to the center post 4, and a peg lead 10.

Follower 6 fits closely between the convolutions of wall 1 which act as a cam operating on follower 6 to guide the wiper 9 over the tops of contact pegs 3 as arm 5 is rotated.

In the embodiment shown in Figure 3, a block of nonconducting material is machined or cast to create an upper integral spiral wall 12 to form a groove or channel 13 in the face of the block of material, the groove 13 being preferably of an Archimedean spiral configuration. Holes are drilled in the groove 13, normal to the surface of the block, so that pegs 14 can be positioned in the block of material, extending entirely through the said block, as shown in Figure 4. A wiper 20 is rigidly at tached to a roller follower 18, which in turn is slidably and rotatably attached to an arm 16 by means of guide portion 19 riding in a longitudinal slot in arm 16. The arm 16 is rotatably attached to the block of material by means of center post 15, so that the wiper 20 will follow a path that passes over all of the pegs 14 when the arm 16 is rotated. Individual peg leads 22 are attached to the pegs 14 and a wiper lead 21 is attached to wiper 20.

The upright walls 1 and 12 of the embodiments shown in Figures 1, 2, 3 and 4 can be eliminated by employing a cam drive, external to the body carrying the stationary contacts, to direct the wiper over a desirable path. Such an arrangement is shown in Figure 5. Here a circular plate 23 is provided with bevel gear teeth 24 on its periphery. In this circular plate 23 are positioned a plurality of contacts 26 so disposed that they preferably form an Archimedean spiral, for example. The circular plate 23 is rigidly maintained in a desired position by means of a rigid connection to a base support 35, through a support column 36. Rotatably disposed with respect to circular plate 23 is a wiper-cam assembly comprised of a hub-block 25, mounted at the center of plate 23, a horizontal shaft 27 rotatably connected to the hub-block 25, a helical cam 28 rigidly connected to the shaft 27 and to a cam extension 31, a bevel gear 32 rigidly connected to the extension 31. Bevel gear 32 meshes with bevel gear teeth 24 on the periphery of plate 23. A guide bar 38 is rigidly connected to the hub-block 25 extending parallel to cam 28 to provide a means of supporting and preventing rotation of a cam follower 29 with respect to the hub-block 25, but which does not prevent a radial translation motion of the cam follower 29. Cam follower 29 carries a contact wiper 30. Translation motion of the cam follower 29 with respect to the hub-block 25, is produced by the rotation of the helical cam 28 by gear 32 when the hub-block 25 is rotated by knob 25a and the wiper-cam assembly. A wiper lead 41 is attached to a wiper lead connector 42 and is therefrom connected to the wiper 36. Contact leads 37 provide an electrical connection to each of the contacts 26.

In operation, the embodiment illustrated in Figures 1 and 2 is connected into a plurality of electrical circuits by means of peg leads 10 and by means of wiper lead 11. A rotation of the arm 5 repositions the wiper 9 such that it makes contact with a different peg 3 thereby causing a change of the circuit being completed by the switch. Since the pegs 3 are in an Archimedean spiral configuration, for example, rather than a circular config uration; a reduction in the physical volume of a multicontact switch is realized.

The device illustrated in Figures 3 and 4 is similar in operation to the device illustrated in Figures 1 and 2. An electrical circuit is completed between a peg lead 22 and the wiper lead 21 through contact between a peg 14 and the wiper 207 A rotation of arm 16 causes roller follower 18 to perform a combination rotation translation motion as prescribed by the spiral configuration of the groove 13. The rotatable connection between the center post 15 and the arm 16 and the slidable connection between the roller follower 18 and the arm 16 is such that a low resistance electrical circuit exists between the roller follower 18 and the center post 15. An electrical circuit can, therefore, be completed between a peg lead 22 and the wiper lead 21.

The embodiment illustrated in Figure employs a spiral configuration of stationary contacts but disposes a cam drive for the wiper contact support above and away from the plate containing, the stationary contacts. Thus a rotation of the control knob 25a rotates the entire wiper-cam assembly. The rotation of bevel gear 32 and its cooperation with gear teeth 24, disposed on the periphery of circular plate 23, rotates the cylindrical cam 28, causing simultaneous radial movement of cam follower 29" and the contact wiper 30. Thus the path of the wiper 30 is such that it traverses a path that includes all of the contacts 26. Due to the spiral arrangement of the stationary contacts of all three embodiments of the invention described herein, the area occupied by such contacts is reduced to a minimum with adequate insulation separation thereof.

From the above description it will be apparent that there is thus provided a device of the character described possessing the particular features of advantage before enumerated as desirable, but which obviously is susceptible of modification in its form, proportions, detail construction and arrangement of parts without departing from the principle involved or sacrificing any of its advantages.

While in order to comply with the statute, the inven tion has been described in language more or less specific asto structural features, it is to be understood that the invention is not limited to the specific features shown,

but that the means and construction herein disclosed comprise a preferred form of putting the invention into effect, and the invention is, therefore, claimed in any of its forms or modifications within the legitimate and valid scope of the appended claims.

What is claimed is:

1. In a switch having a body of insulating material provided in one face with a series of spirally arranged fixed contacts and a rotatable arm pivoted at the center of the spiral with a contact member movable therealong to sequentially engage said fixed contacts; an upstanding spirally arranged wall separating one turn of the contacts from the next and constituting a cam, a roller follower having its axis normal to the rotatable arm and guided for spiral movement by said cam; an axially projecting necked portion slidable and rotatable in a longitudinal slot in the pivoted arm; and means rotatably and slidably mounting said follower on the rotatable arm.

2. In a switch having a body of insulating material provided in one face with a series of spirally arranged fixed contacts and a rotatable arm pivoted at the center of the spiral with a contact member movable therealong to sequentially engage said fixed contacts; an upstanding spirally arranged wall separating one turn of the contacts from the next and constituting a cam, a roller follower having its axis normal to the rotatable arm and guided for spiral movement by said cam; a necked portion of said roller follower on the side adjacent the rotatable arm projecting axially from the roller and slidable and rotatable in a longitudinal slot in the pivoted arm, and a wiper member mounted on, and projecting axially from said roller follower to the side remote from said rotatable arm to make wiping contact with the fixed contacts.

References Cited in the file of this patent UNITED STATES PATENTS 454,816 Ward June 23, 1891 1,409,879 Manley Mar. 14, 1922 1,589,159 Henriquez et al. June 15, 1926 1,770,000 Kuhlman' July 8, 1930 2,030,369 Heintz Feb. 11, 1936 2,398,994 Bazley Apr. 23, 1946 FOREIGN PATENTS 319,861 Great Britain Oct. 3, 1929 

